Central Intelligence Agency Director William J. Casey, whose memory ranges from weak to nonexistent on unauthorized disclosure of President Carter's briefing books to the 1980 Reagan campaign, is worried that fellow Reaganites are a bunch of blabbermouths.

Appearing before the senior White House staff last Tuesday and reading a prepared lecture in a tone described as "an admonishing mumble," Casey fretted about the difficulties of keeping classified information classified.

In the process, he gave several still-classified examples of "unauthorized disclosures" to staff members not normally authorized to receive classified information of any kind.

Fortunately for the security of the republic, Casey's examples included such previously rehashed events as the thwarted Libyan invasion of the Sudan, the world-publicized sending of arms to Afghan guerrillas and the open secret that the United States is assisting anti-government rebels in Nicaragua.

All of this was old hat. But some of the White House staff members were startled to hear Casey's report on care and feeding of the National Intelligence Daily, the comparatively low-level CIA analysis provided daily to 150 U.S. government officials. A legend on the cover of this document, known as NID, says it is to be returned the same day and not to be duplicated.

According to Casey, a CIA check showed that more than 100 of the documents were not being turned in and that some of those returned came complete with handy notations instructing secretaries to copy them. One responsive official, asked to return his copy, supposedly gave back 75 photocopies.

As it turns out, there are remedies to deal with such carelessness.

Casey mentioned a few of them, such as dismissal and administering lie-detector tests to employes who engage in "unauthorized disclosures." As far as is known, he would make an exception for briefing material that mysteriously appears on the desk of campaign chairmen just before a crucial debate.

Two days later, when asked to provide details of how the Carter briefing book wound up in the Reagan camp, Casey gave an impressive demonstration of what a CIA director might do if he became a prisoner of war.

Although he provided his name and rank, Casey said he remembered nothing whatever about a briefing book that White House chief of staff James A. Baker III recalled Casey giving him. Casey's recollection has not improved subsequently.

Most Americans would, of course, be genuinely concerned by disclosure of real national-security secrets by those charged with keeping them. But some in the White House believe that national security in the Reagan administration would be served especially well by appointment of a CIA director who starts with a greater presumption of credibility.

That is not Casey's long suit, as a couple of jokes making the White House rounds last week attest. One, attributable to Alan Abelson in Barron's, said "CIA" really stood for "Casey Investing Again," a reference to the remarkable timeliness of the director's successful stock-market investments.

The other, repeated on background and presumably not classified, was a tongue-in-cheek assurance that Casey could not have been the recipient of the Carter briefing book.

"If Bill had received it," one White House official said, "he would have placed it in a blind trust."

Remember when candidate Reagan made fun of Occupational Safety and Health Administration pamphlets that told one how to climb a ladder safely? President Reagan is at it again. Last Monday in Jackson, Miss., he took pride in cancellation of a federal publication that he said was called "How To Have A Sparkling Clean Sink."

"Now the very top of this illustrates why they had to keep this bulletin out for you people," he said.

"It said, 'a clean sink helps keep you and your family healthy. A dirty sink often smells bad. It will attract bugs . . . . ' And the last point is, 'A clean sink looks nice.' Now you ladies know you would never have thought of that by yourselves if the government hadn't pointed it out to you."

In the same speech, Reagan used the term "feet people" to describe what he said would be a tidal wave of refugees flooding into the United States if Marxist governments take over in Central America. It apparently is a variation on the long-used phrase "voting with one's feet," used chiefly to describe refugees who fled from Soviet-bloc countries to Western Europe.

The first known mention of "feet people" appeared in a Conservative Digest news release by Richard A. Viguerie on April 28.

It apparently found its way into the speech through the services of conservative speech writer Dana Rohrabacher, who is said, in a popular administration phrase, to have "no recollection" of where it came from.

Best White House press corps line of the week came from Joe Ewalt of RKO General, who said: "The feet people will be fleeing the Sandal-istas."

Reaganism of the Week: (From a speech to the American Medical Association in Chicago): "I think sometimes we want health and we don't want public hazards, dangers to our people, whatever they may be, but a very eminent scientist once said that he questioned whether there were any dangerous or harmless substances. He said there were only dangerous or harmless amounts. And I think that sometimes we have with the fantastic and the dramatic, melodramatic treatment of some of these things, we frightened a great many people unnecessarily. The answer is not to take risks, not at all, but to make sure also that we haven't frightened people unless there is truly a reason for them to be frightened."